Once more, with feeling...

3-C-1-b-(1)-(a)
3 out of first 5: After 2 unused SC/FSB, the next three increase your MPG by 1 hour, regardless of assigned or picked up.

3-C-1-b(1)-(b)
Assigned after 5: After 5 unused SC/FSB that were assigned by the crew desk, each subsequent one assigned that goes unused increases MPG by an hour.

So if you pick up 10 SC and they all go unused, your MPG goes up by 3. (3 out of first 5)

If desk assigns you 10, you get 3 (3 out of first 5) plus another 5 (assigned after 5) for 8 total.

Also be aware that the definition of a used shortcall is a trip that departs within 13 hours of the assignment being made (put in your schedule). They have a nasty habit of putting it in there 13+ while you're in crew rest and notifying you at the start of your RAP, which is not the intent of SC. PDR that with CCS alerting message times for credit.